Using generator to charge batteries direct

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marekp asked Jul 6, '20

Using generator to charge batteries direct

Friend of mine "donated" to my Victron setup very nice diesel generator.

It is a military surplus 7.5kW unit in very good condition.

My Victron setup (under development) consists of two MultiPlus-II 48/3000/35-32 and one EasySolar-II GX 48/3000/35-32 connected in 3-phaze configuration.

48V/200Ah LFP battery.

Now there are two problems to overcome with this generator.

1. It is 115V unit and my grid is 230V.

2. It is 400Hz model. :(

I cannot use it as strait source of AC but I can make it into 65A DC generator.

Two questions.

1. Is there a of the shelf Victron LFP battery charger that I can use with this generator?

2. Can I connect it to the MPPT 250/70 that I have in EasySolar unit? Of course after converting it do a DC source.

battery charging Generator

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klim8skeptic ♦ commented · Jul 06, 2020 at 11:17 AM

Pretty sure that you can not gang (parallel/multi phase) non identical multi units.

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lklmenterprises klim8skeptic ♦ commented · Jul 06, 2020 at 12:02 PM

Correct - the supported configuration is for 3 identical units - I have a feeling that the EasySolar 3000 is a full MultiPlus II.

I have an EasySolar 1600 - however that is the Multi Compact, but I was told the 3000 are Full Multi's

The main selling point of the EasySolar is just the adsition of the Larger case that includes a breaker board and MPPT controller inside it.

I could be wrong of course, but disclaimer is that was what I was told...

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marekp klim8skeptic ♦ commented · Jul 06, 2020 at 12:20 PM

They are identical Multuplus-II, only one of them (EasySolar-II) has MPPT and GX added.

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marekp commented · Jul 10, 2020 at 09:11 AM

Thank all for the comments to my post, but my two main questions are left unanswered.

1. Is there a of the shelf Victron LFP battery charger that I can use with this generator?

2. Can I connect it to the MPPT 250/70 that I have in EasySolar unit? Of course after converting it do a DC source.

The first one is probably answered by a Victron product line catalog.

I found only one charger (Skylla 48/25 TG) that takes DC input and charges 48V battery pack but its DC voltage input starts around 180V. If I load my generator with 65A it will, for sure, drop below 180V. Also I am not sure if it can be used with LFP batteries.

The second question. I think, should answered by Victrons pro because is about use of MPPT charger with other than PV source of DC power.

Can I count on the answer from Victron?

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Answer 1 · 2020-07-06T12:22:16Z

lklmenterprises answered · Jul 06, 2020 at 12:22 PM

Ex MilSpec and 400hz tells me it is potentially an Airforce or naval GPU (Ground Power Unit.) - so the AC Generation is 3 Phase? and it already has a DC generation circuit?

The issue you will have with running into the MPPT off DC is you need +5v above your battery voltage for the MPPT to start charging.

So if you have a 48v LFP - that will sit around 52v at storage you would need 57v DC at the generator just to get to Storage, and in order to hit Absorption of 57.6v - you would need 62v. So if it can deliver that, you are laughing...otherwise - depending on the Genset, you may be able to keep the Motor as is, and swap the Generator out of it.

We had a 15Kva Monster on a farm that was 3Phase (230v/415v) - It had a DC communtator on the flywheel right next to the AC we used the Solar battery bank to power the commutator to start it up, but without the appropriate electronics (Buckboost) we couldn't use it to charge the bank as the bank was 24v and we could only get 14v out of it.

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marekp commented · Jul 06, 2020 at 12:45 PM

This generator i 1-phaze 115V AC and 65A.

To make it DC I will add rectifier and capacitor.

Under load the voltage will be above 115VDC. Without load around 200V DC.

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gen-tab-gs.jpg (525.1 KiB)

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